1. Field of Invention
The present invention relates to a fastening element for use in setting tools and having a stem provided at its opposite ends with a tip and a head, respectively, with the head being covered by a cover element.
2. Description of the Prior Art
Setting tools for driving fastening elements in a substrate include a drive piston that impacts a fastening element for driving the fastening element in. The problem with the drive piston consists in that metallic impacts of the piston on the to-be-set fastening elements, e.g., bolts or nails lead to a high wear of the piston. In setting tools having a small power, e.g., in combustion-engined setting tools, the wear of the piston tip or end is a primary reason of the piston failure. As a result, because of a rapid wear of the piston, the setting tools should be designed so as to insure an easy replacement of the drive piston. This results in high costs of the setting tools and in high maintenance costs as the drive piston should be replaced often.
U.S. Pat. No. 2,140,749 disclose a manually driven-in nail the head of which is covered with a coating. The coating remains dry at a normal room temperature. However, under higher temperatures, the coating becomes sticky. Such nails are used, e.g., in roof covering when, simultaneously with driving-in of a nail, sealing of the entry opening of the nail against the nail head should take place in order to prevent penetration of moisture. In the known fastening elements, the cover or the coating is removed, after the setting of a fastening element, only with much difficulty. However, in many applications, in which the fastening elements are driven in with a setting tool, it is required that no soft or sticky coating remains on the head of a fastening element. Accordingly, an object of the present invention is to provide a fastening element in which the above-discussed drawbacks of conventional fastening elements are eliminated and which can easily be used in a setting tool.
This and other objects of the present invention, which will become apparent hereinafter are achieved by providing a separate cover element that is detachably arranged on the head of a fastening element.
A separate cover element, which, during a setting process, absorbs the setting energy by being deformed, noticeably reduces the wear of the drive piston. Likewise, by forming the cover element as a detachable element, it is easily removed from the head after the setting process, without leaving any residue.
Advantageously, the cover element is provided with stud or a clip element for being releasably secured to the head of a fastening element. The provision of the stud or clip element insures that the cover element does not become lost during transportation, while still being easily removable from the head after the setting process.
Advantageously, the fastening elements can be assembled into a magazine by connecting separate cover elements with each other. In this case, additional elements for forming the magazine of fastening elements are not needed.
According to a further advantageous development of the present invention, the cover element is provided with a holding element that permits to releasably secure the cover element to the head of a fastening element. This holding element can be formed as a stud engageable in a groove formed in the fastening element head.
According to another advantageous development of the present invention, the holding element can be formed as a collar provided at the edge of the cover element and with which the cover element can be clipped on the head of a fastening element.
Advantageously, a strip of cover elements with the cover elements is secured not to the fastening elements but rather is provided with braces or/and webs with which the cover element strip is mounted on another magazine strip that encompasses the stems of the fastening elements. During the setting process, the webs are automatically teared off, whereby the separation of the cover element from the second magazine strip takes place automatically.
Advantageously, cover elements are formed of a plastic material, which substantially reduces the wear of the setting direction end of the drive piston. Instead of the plastic material, other deformable materials, e.g., light metals, can be used.
According to the present invention, between the cover elements of a cover element strip, there are provided weakness arears or break-off points, which insure an easy separation of the cover elements from the cover element strip during a setting process.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.